Evaluation of a Proposed In Vitro Test Strategy using Neuronal and Non-neuronal Cell Systems for Detecting Neurotoxicity

Abstract

The European Commission White Paper, "Strategy for a future chemicals policy" (EC, 2001) is estimated to require the testing of approximately 30,000 "existing" chemicals by 2012. Recommended in vitro tests require validation. As the White Paper (EC, 2001) requires neurotoxic data, this study evaluated an in vitro testing strategy for predicting in vivo neurotoxicity. The sensitivities of diVerentiated PC12 cells and primary cerebellum granule cells (CGC) were compared to undiVerentiated PC12 cells which can indicate basal cytotoxicity. Cytotoxicants and neurotoxicants selected for testing covered a range of mechanisms and potencies. Neurotoxicants were not distinguished from cytotoxicants despite signiWcantly diVerent cell system responses using all endpoints; cell viability/activity, ATP depletion, MMP depolarisation, ROS production and cytoskeleton modiWcations. For all chemicals tested, neuronal-like cell systems were generally less sensitive than undiVerentiated PC12 cells. Acute oral rodent LD50 values correlated with cytotoxicity IC50 values for the respective chemicals tested in each cell system. This study concluded that although simple non-speciWc assays are required to distinguish basal cytotoxicity from speciWc neurotoxicity by using diVerent cell systems with diVerent states of neuronal diVerentiation, further work is required to determine suitable combinations of cell systems and endpoints capable of distinguishing neurotoxicants from cytotoxicants.